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Arlo 06-11-2008 12:11 AM

Ceramic Floor Tile Spacers
I am planning to DIY ceramic floor tile in my master bath. I've done it once before with great results many years ago. I plan to put 1/4" cement board over the subfloor. I was recently scouting the supplies at the store and saw they have many different sizes of spacers. I assume the really small spacers are used to tile bathroom walls. What would be the smallest spacer I could use on a floor? I like the look of a really thin grout line. Is there any reason this would be a bad idea?

Termite 06-11-2008 12:21 AM

Let me change the subject on you for just a second. You need to use 1/2" backerboard under floor tile. 1/4" would be a no-no for sure.

As for spacers, use whatever you like, as long as you can get the grout into the gap. You MUST fill the gap with grout. There's rules of thumb, but there are no set rules!

angus242 06-11-2008 12:52 AM

For ceramic on the floor, I like to use not bigger than 3/16". However, depending on the edge of the tile, I might not go smaller than 1/8". I think 1/16" only looks good on wall tile or honed/polished stone floor tile. That's just me.
Oh, and 1/4" backer IS made for floors. 1/2" is for walls.

Make sure you use thinset between the backer and subfloor, staggering the seams. Screw or nail (alkali-resistant fasteners) it down. Now tape the seams with an alkali-resistant tape set in thinset. Now you can tile.

OR apply a layer of Ditra over the backer and THEN tile for an even better installation! Ditra can be found at Home Depot and is usually around $1.55USD per sq ft.

Make sure you use a quality thinset approved for your application. Read the specs on your backer or the Ditra (hint, hint) to get the appropriate modified or non-modified version.

Good luck!

Termite 06-11-2008 08:14 AM

OK, I stand corrected, sort of. I guess I see it as a best practice to use 1/2" backer under floors, although 1/4" can definately be used. I should have made that clear. 1/2" backer is in fact made for floors as well as walls. Hardie's installation instructions require a floor deflection of L/720 for stone tile. That is stiffer than 95% of homes' floor systems are designed. They also allow installation of 1/4" backer over rated sheathing spanning 24" between floor joists...Not good. Although the deflection rating is a factor of the entire floor systems load and composition, I'll always advocate the thickest backer possible to achieve the stiffest/strongest assembly.

angus242 06-11-2008 09:51 AM

Backer boards were not designed nor intended to be structural panels and provide no structural value. If you're trying to achieve a better deflection rating, you need to look elsewhere for more support!
1/2" backer just gives you a "taller" floor. :thumbsup:

HomeDepot23 06-15-2008 09:10 AM

Carpet installers hate the backerboard. We have to find a way of shimming our carpet to meet the tile. So given the choice of 1/4" or 1/2" we want the 1/4" every time.

As far a spacers. I get told time and time again that Home Depots cheap 16" tile is never square or are different sizes up to 1/8" in difference from one tile to another, so a small spacer like 1/8" will make your life so much harder.

I would normally go 3/16" like Angus said, or 1/4" worst case if the tiles seem irregular. Just remember the bigger the grout line, the more cleaning you have to do and the less beautiful tile you actually get.

MinConst 06-15-2008 07:38 PM

Being a man of all trades I do lay quite a bit of tile. Mostly here in Florida on concrete so I won't get into the backer board part. I have stopped using spacers. They do their job of making each joint even but when you run into a tile that is under size the rest of the job follows. I find it better to eyeball the space to make them as even as possible making up for the imperfections in the tiles. In the end the job has neater lines and a better look.

Arlo 06-15-2008 10:08 PM

Thanks for all the input!

javan 06-18-2008 12:31 PM


I did my bathroom floor with that stuff. Wow, so nice. Easy to install too!!!

Bud Cline 06-18-2008 05:27 PM


For a "building codes guy" you sure appear to be misinformed about several things. Where does your information and training come from?:)

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